The present invention relates to an apparatus for sensing tension in a seat belt.
A typical occupant restraint system for a vehicle includes a seat belt that has opposite ends anchored to the vehicle and is extensible about the occupant. The seat belt thus helps restrain the occupant in the event of a vehicle collision or a sudden deceleration of the vehicle. Seat belts are also used to help secure child safety seats in the vehicle seat. When using a seat belt to help secure the child safety seat, it is common to draw the seat belt tight in order to secure the safety seat tightly in the vehicle.
It is known to use one or more sensor apparatuses in conjunction with an inflatable vehicle occupant protection device for helping to protect an occupant of a vehicle. The sensor apparatus provides information to a controller that controls the inflation of the inflatable vehicle occupant protection device in accordance with conditions sensed by the sensor apparatus. One such condition is the weight of the person or object occupying the vehicle seat.
In accordance with the present invention, an apparatus includes a first member and a second member connected to the first member. The first and second members are pivotable relative to each other about an axis. Biasing means biases the first member to pivot in a first rotational direction relative to the second member about the axis. A vehicle seat belt engages the first member and urges the first member to pivot against the bias of the biasing means in a second rotational direction about the axis, opposite the first rotational direction, as tension in the seat belt increases. This causes the relative angular position of the first and second members to change in proportion to the amount of tension on the seat belt. The apparatus also includes means for measuring the angular position of the first member relative to the second member. The means provides a signal that corresponds to the angular position of the first member relative to the second member. The signal is proportional to the amount of tension in the seat belt.